Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$176.93	11.357%	$197.0239	$197.02	$197.00	$197.00
Purchase #2	$81.38	10.434%	$89.8712	$89.87	$89.85	$89.90
Purchase #3	$94.62	9.802%	$103.8947	$103.89	$103.90	$103.90
Purchase #4	$87.98	11.229%	$97.8593	$97.86	$97.85	$97.90
Purchase #5	$129.33	8.720%	$140.6076	$140.61	$140.60	$140.60
Purchase #6	$142.69	8.409%	$154.6888	$154.69	$154.70	$154.70
Purchase #7	$40.97	11.232%	$45.5718	$45.57	$45.55	$45.60
7 purchase totals =	$753.90		$829.5173	$829.51	$829.45	$829.60